The objective is to determine the biomechanical and neurophysiological relationship between the intrinsic laryngeal muscles for speech, voice, respiration, and swallow. Disorders such as spasmodic dysphonia and voice tremor are also being studied by the same procedures. The thyroarytenoid (TA) and cricothyroid (CT) muscles are highly related in their change in activation over time for all actions in normal speakers. The ratio of percent increase in the TA over the CT Is between 0.7 and 1.2 in normal volunteers and between 2 and 12 in spasmodic dysphonia. These patients have heightened TA over CT activation in respiration, swallow and speech. Other abnormalities found in spasmodic dysphonia include: prolonged muscle activation times prior to speech onset and spasmodic bursts in both the TA and CT muscles during speech. The validity of a new non-invasive pharyngeal-esophageal surface electrode for recording activity from the posterior cricoarytenoid (PCA) was demonstrated In 60% of the subjects tested. Future studies will compare the percent activation between the PCA, the major vocal fold abductor, and the TA and CT in norma speakers and patients with adductor and abductor spasmodic dysphonia.